Implantable medical devices for producing a therapeutic result in a patient are well known. Examples of such implantable medical devices include implantable drug infusion pumps, implantable neurostimulators, implantable cardioverters, implantable cardiac pacemakers, implantable defibrillators and cochlear implants. Of course, it is recognized that other implantable medical devices are envisioned which utilize energy delivered or transferred from an external device.
A common element in all of these implantable medical devices is the need for electrical power in the implanted medical device. The implanted medical device requires electrical power to perform its therapeutic function whether it be driving an electrical infusion pump, providing an electrical neurostimulation pulse or providing an electrical cardiac stimulation pulse. This electrical power is derived from a power source.
In some implantable medical devices electrical power can be transcutaneously transferred through the use of inductive coupling. Such electrical power or energy can optionally be stored in a rechargeable battery. In this form, an internal power source, such as a battery, can be used for direct electrical power to the implanted medical device. When the battery has expended, or nearly expended, its capacity, the battery can be recharged transcutaneously, via inductive coupling from an external power source temporarily positioned on the surface of the skin.
While many devices and techniques have been developed to provide transcutaneous energy transfer in order to power an implantable medical device and/or charge or recharge a battery associated with an implantable medical device, external chargers associated with such devices are sometimes cumbersome and generally require the patient to take some overt step in order to associate an external charger in proximity with an internal, secondary coil associated with the implanted medical device and to initiate steps and/or procedures to accomplish a transcutaneous energy transfer in order to charge or recharge the implanted medical device. In some cases, this may require the patient to consciously remain in contact with or in the proximity of the external charging device. Such charging techniques and equipment tend to limit the flexibility and/or mobility of the patient having an implanted medical device while the device is charging.
U.S. Patent Application No. US 2003/0078634 (A1), Schulman et al, Full-Body Charger For Battery-Powered Patient Implantable Device, attempts to solve the problem of a patient having multiple implanted devices to be recharged. Schulman et al '634 discloses a full-body charger for charging one or more battery-powered devices wherein such devices are configured for implanting beneath a patient's skin for the purpose of tissue, e.g., nerve or muscle, stimulation and/or parameter monitoring and/or data communication. A support structure, typically chair-shaped or bed-shaped, capable of supporting a patient's body while providing a magnetic field to one or more of the implanted devices using one or more coils mounted within for providing power to the implanted devices. As a result, a single, generally sequential, charging cycle can charge all of the implanted devices and thus minimize the charge time requirements for a patient and accordingly improve the patient's lifestyle.
U.S. Pat. No. 6,212,430, Kung, Electromagnetic Field Source With Detection of Position of Secondary Coil In Relation To Multiple Secondary Coils, attempts to locate a secondary coil associated with a particular implanted medical device. Kung discloses an electromagnetic field source for providing electromagnetic energy to a secondary coil, including two or more primary coils that each carry a time-varying current to produce an electromagnetic field, and a controller that selectively provides current to one or more primary coils based on their position with respect to the secondary coil. The secondary coil may be implanted in a human recipient and used to provide power for the operation of a medical device, such as an artificial heart or ventricular assist device. The primary coils may be housed in furniture. For example, they may be housed in a bed mattress or mattress pad on which the recipient rests, or in a blanket for covering the recipient. The controller includes a proximity detector that identifies those primary coils that are closest to the secondary coil, and a current director that, responsive to the proximity detector, selectively direct time-varying current though the closest primary coils.